Centrifugal switch for electric motors.



K. TORNBERG. CENTRIFUGAL SWITCH FOR ELECTRIC MOTORS.

APPLICATION FILED JULY 10 1905.

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PATENTED JUNE 11, 1907.

UNITED srnries KNUT TORNBERG, or LYNN, MASSA PATEN QFF CHUSETTS,ASSIGNQR T GENERAL ELECTRIC ooMriiNY, A'CQBPORATIUN or NEW YORK.

QENTRIFUGAL snares FOR ELEGTREG morons.

Specification of Letters Patent.

Patented am 11, 1907.

Application filed July 10,1905. Serial lilo. 268,951.

To, all whom it may concern:

Be it known that I, KNUT TORNBERG, a

citizen of the United States, residing at Lynn,-

county of Essex, State of- Massachusetts, have invented certain new anduseful .Im-

'prove'ments in Centrifugal Switches for Elec- 'tric Motors, of whichthe following is a specification. Y

My inventionrelates to centrifugally-actuated switches for'electricmotors, and is particularly adapted for use in" connection withinduction motors of the type designed to start with the resistance inseries with the rotor winding and toj run when up to speed with theresistanceshort circuited.

Numerous types of centrifugally-actuated switches have been designedheretofore for the purpose of short-circuiting the rotor resistanceautomatically when .a predetermined speed is'reache'd.

My invention relates to. this type of iswitcli and its object is toprovide a novel arrange ment of the switch, whereby a number ofadvantageous features are obtained which arenot present-in such switchesas heretofore, constructed.

- axOne feature ofiny invention consistsin so in so arranging thecontactcarried bythe cuite'd,

mounting the contactcarried by the centrifugally-movable' member of theswitch that it is moved by said membersubstantially at right-angles to acentrifugal direction, and is capable of movement in a centrifugaldirection relative to said. member, and arranging the contacts to beengaged by the first contact so as to receive the'pressure due to thecentrifugal force of thefirst contact. By

means of this arrangement the pressure between the electrical contactsis in no wise dependent upon the centrifugal force of the actuatingmember, so that the centrifugal force of the actuating member auditsrestraining spring may be correlated asdesired, without affecting thepressure between the electrical contacts. r

My invention further comprises so arranging' the contacts that theresistances connected to the several phases-of the rotor windingalwaysbe simultaneously short-cir- Another feature ofmy inventionconsists centrifugally-movable member that it is self-alimng.

Another feature of my invention consists in providing a catch engagingthe centrifugal its movement until the centrifugal force reaches apredetermined amount. By this means a more positive action at a moredefinite speed is obtained than in former structures.

trifugal movement. E represents a leafspring, secured at oneend' to thecentrifugally-movable member C, providedwith an adjusting screw e, andcarrying at its free end a contact bears against a slide or guide G. Itwill be seen that the spring Eforms a connection between the member Cand contact F, which is ada ted to permit a centrifugal movement whilethe centrifu al movement of the mem' ber C will move t e contact F in asubstantially circumferential direction along the The slide over whichthe contact the plate A. With this arrangement it will be seen that whenthe centrifugal member C is thrown outward by centrifugal force, thecontact F will be moved along the slide so as to engage the contacts H.The pressure with which contact F will bear upon contacts-H depends onlyupon the speed of the motor and the weight of contact In other words, itis entirelyindependent of the centrifugal force of the actuating memberand the restraining force of the spring Time My inventio'nwill best beunderstood by of t e contact F relative to the member C,

guide G. 4

7 moves is formed in two portions, one of which comprises the contactsH-su ortedon and insulated from a projection from member at starting andadapted to restrain able actuating member'of. the switch, which ispivoted on the plate A at c, and is prov ded with a restra1rung-spr1ng Dopposing-- its cen- F, which,-whenthe motor isat rest v F bridges thecontacts H all three simultaneously. The contacts H H are two latterforcesF-maylbe adjusted as desired, without in any way altering theeffective pressure between electrical contacts.

The contact F is pivotally mounted on the end of the spring E, as isclearly shown in Figs. 1 and 2, so that this contact is selfalining. Thetwo contacts H are alined'in axial direction, as clearly shown in Fig.2, so that the contact block F necessarily engages both contacts Hsimultaneously. As will presently be seen, this results inshort-circuiting all the phases of the rotor winding provided with leads7: connecting them to the rotor winding, while the contact F ispreferably grounded either through its support or by means of a flexiblelead I11 order to obtain a more positive action of the switch I providein addition to the usual restraining spring D a spring catch I adaptedto engage the centrifugally-movable member 0 only at starting. Thiscatch serves to restrain the member 0 'against movement until itscentrifugal force reaches a predetermined amount. When this amount isreached the member C. slips past the catch I and moves quickly to itsextreme odtward position. This snap-action is assisted by the frictionof contact-block F on the slide G.

Now, referring to Fig. 3, M represents the primary winding of the motor,which is supplied with threehase current from any suitable sourceindicated by the line-Wires 1, 2 and 3. on re resents the rotor orsecondary winding 0 the motor, which is shortcircuited through thestarting resistance R. In this figure two of the terminals of thewindings m are connected by suitable leads directly to the resistanceand the third terminal is connected through a ground connection. Thecontact H 'of the centrifugallyactuated switch is connected to the twoformer terminals, and the contact-block F' is connected through groundto the. third terminal. Consequently, when contact-block hases of therotor winding are short-circuited, and since the contacts H are arrangedto be engaged simultaneously by the block F, as shown in Fig. 2, allthree phases are shortcircuited simultaneously.

Although I have shown my invention as applied to a three-phase inductionmotor, it wi be understood that it is not limited to a motor of thisparticular type. Furthermore, my invention comprises a number of.

features which, while I prefer to use them together, may be usedindependently, and which I desire to claim whether used together or not.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In amotor, a centrifugally-actuated switch carried by the motor arirature comprising a centrifugally-movable member, a

switch contact operated by said member, a

permit a centrifugal movement of said contact relative to said member, aslide adapted to betraversed by said contactwhen moved eircumferentiallyand to restrain it against centrifugal force,'and a switch contactconnected to the armature windingof the motor and forming a portion ofsaid slide.

2. In a motor, a centrifugally-actuated switch carried by prising acentrifugally-movable member, a leaf spring secured at one end to saidmember and extending in a substantially circumferential direction, acontact carried at the free end of said spring, a slide adapted to betraversed by said contact and to restrain it against centrifugal force,and a contact connected to the motor armature comthe armature winding ofthe motor and forming a portion of said slide- 3. In a motor, acentrifugally-actuated switch carried bythe motor armature comprising acentrifugally-movable member, a leaf spring secured at one end to saidmember and extending substantially at right angles to a centrifugaldirection, a contact carried at the free end of said spring, a slideadapted to be traversed'by said contact and to restrain itagainst-centrifugal force, and a contact connected to the armaturewinding of the motor and forming a portion of said slide.

4. In a motor, a centrifugally-actuated switch carried by the motorarmature comprising a centrifugally-movable member, a self-aimingcontact carried by said member, a connection between said contact andsaid member adapted to permit a centrifugal movement of said contactrelative to said member and to move said contact substantially at rightangles to a centrifu al direction when said member is moved, a slideadapted to be traversed by said contact when moved, and a contactconnected to the armature winding of said motor and forming a portion ofsaid slide.

5. In a motor, a centrifugally-actuated switch carried by the motorarmature comprising a centrifugally-movable member, a leaf springsecured at one end to said member and extending substantially at rightangles to a centrifugal direction, a self-alining contact carried at thefree end of said spring, a slide adapted to be traversed by said contactand to restrain it against centrifugal force, and a contact connected tothe armature winding of the motor and forming a portion of said slide.

6. In a motor, a centrifugally-actuated switch carried by the motorarmature comprising a centrifugally-movable member, a contact blockcarried by said member and contacts connected to the armature winding ofthe motor and adapted to be bridged by said contact block;

8. In a motor, a centnfugally-actuated switch carried by the motorarmature com-- prising a centnfugally-movable member, a

self-alining contact block carried by said member, a connection betweensaid contact and said member adapted to permit a centrifugal movement ofsaid contact relative to said member and to move said contactsubstantially at right angles to a centrifugal direction when saidmember is moved, a slide adapted to be traversed by said contact whenmoved, and pair of alined contacts connected to the armature winding ofthe motor and adapted to be bridged by said contact block.

9. In a motor, a centrifugally-actuated switch carried by the motorarmature comprising a c'entrifugally-movable member, a

- catch adapted to engage said member at starting only and to restrainit from movement until the centrifugal force of said member reaches apredetermined amount, a contact carried by said member, and a secondcontact connected to the armature winding of the motor and adapted to beengaged by the first contact.

10. In a motor, a centrifugally-actuated switchc'arried by the motorarmature comprising a centrifugally-movable member, a spring secured tosaid member and opposing its centrifugal movement, a spring catchengaging said member at starting only and adapted .to restrain itfrommovement until the centrifugal force of said member reaches apredetermined amount, a contact carried by said member, and, a secondcontact connected to the armature winding of the motor and adapted to beengaged by the first contact.

11. In an induction motor, a resistance connected in series with themotor winding, a centrifugally-movable member carried by the rotor, acontact block'carried by said member, a connection between'said contactblock and said member adapted to permit a centrifugal movement of saidcontact block relative to said member and to move said contact blocksubstantially at right'angles to a centrifugal direction when saidmember is moved, a slide adapted to be transversed by said contact blockwhen moved, and a pair of short-circuiting contacts connected to saidresistance and forming a portion of said slide.

12. In an induction motor, a resistance connected in series with therotor winding, a centrifugally-movable member carried by the rotor, acontact block carried by said member and adapted to be moved by saidmember in a substantially circumferential direction, anda pair ofaxially-alined short-circuiting contacts connected to said resistanceand adapted to be bridged by said contact block:

In witnesswhereof, I have hereunto set my'hand this thirtieth day ofJune 1905.

KNUT TORNBERG.

Witnesses:

JOHN A. MCMANUS,J1., HENRY O. WESTENDARP.

